The long-term objectives of this project are to describe (1) the subdivisions of auditory cortex in primates, (2) their connection patterns with the frontal lobe and limbic system, and (3) the convergence of visual and auditory pathways. All three objectives will be investigated by combining microelectrode recordings and anatomical techniques in parallel experiments on New World owl monkeys (for their relatively unfissured and easily accessible cortex), and Old World macaque monkeys (for their close phylogenetic relation to humans). A major focus of this project is to study the cortical and thalamic connectivity of AI, R (or RL), and the surrounding auditory belt cortex. This will be accomplished by placing injections of 2-3 different tracers into AI and R using best frequency maps, and single neuron selectivities to sound direction and level to identify injection sites. The results will provide information on the topographic organization of thalamic and cortical connections of AI and R with respect to tonotopic organizations and representations within an isofrequency contour. Subdivisions of the belt cortex defined by their connection patterns with AI and R, will then be injected and their connections with more distant areas of auditory cortex, frontal lobe and limbic structures examined. The data gathered from these multiple injections in the belt cortex and adjacent auditory fields, will lead to the third major goals of this project, which is to define areas of convergence of visual and auditory information. In these experiments, injections of different tracers in regions of cortex identified as visual or auditory by electrophysiological recording and/or connections with physiological maps of visual and auditory cortex will provide information on the origin and interaction of the two sensory systems in the cortex and thalamus of primates.